Shelf Sea Biogeochemistry blog

Sunday, 30 November 2014

Last of the Snowcatchers

Ocean research cruise blog of Jonathan Sharples

The weather eased off very quickly during yesterday, ending up with
winds less than 10 knots. We arrived back at the mooring site in the
central Celtic Sea and began a last set of sample collection and
experiments, mainly focused on the zooplankton and on the particles
settling down through the water.

The Marine Snowcatcher worked well. We’re getting better at operating
it, though we think that is mainly a result of calmer weather. We are
still not completely convinced that the deeper samples collected with
the Snowcatcher are always from the depth that we think we have
triggered the catcher to shut – if the ship is pitching at all it’s
possible for the catcher to shut while it is being lowered through the
water to the sample depth. However, we can solve that by collecting
nutrient and salt samples from the catcher and comparing those with what
we see in the CTD data to tell us the depth that the Snowcatcher sample
was really taken.

last snowcatcher

Elena Garcia-Martin, from the University of East Anglia, and Darren
Clark, from the Plymouth Marine Laboratory, are working on last these
samples. They are measuring how the different sizes of particles, and
their different components (carbon, nitrogen phosphorus), and being
recycled by bacteria. The deep bacteria are acclimatised to darkness, so
they have to be collected after sunset, extracted from the Snowcatcher
carefully so that they don’t get fried by the ship’s deck lights, and
taken into a darkroom laboratory for analysis.

Elena and Clare sampling particles

One last set of measurements to do here this morning, then we head
off towards Plymouth. Should arrive just south of the Eddystone
lighthouse about 0600 tomorrow.